Power converting device

ABSTRACT

The device includes a rectifier circuit that converts alternating-current power from an alternating-current power supply into direct-current power; a short-circuit unit that short-circuits the alternating-current power supply via a reactor connected between the alternating-current power supply and the rectifier circuit; and a control unit that controls an ON/OFF operation of the short-circuit unit during a half cycle of the alternating-current power supply. The control unit includes a driving-signal generating unit that generates a driving signal Sa that is a switching pulse to control the ON/OFF operation of the short-circuit unit; and a pulse dividing unit that divides the driving signal Sa into a plurality of switching pulses.

CROSS REFERENCE TO RELATED APPLICATION

This application is a U.S. national stage application ofPCT/JP2014/075676 filed on Sep. 26, 2014, the contents of which areincorporated herein by reference.

FIELD

The present invention relates to a power converting device that convertsalternating-current power into direct-current power.

BACKGROUND

The conventional technique described in Patent Literature 1 belowdiscloses a power-factor improving circuit that improves the sourcepower factor to reduce harmonic components contained in the inputcurrent and that selects a full-wave rectification mode or adouble-voltage rectification mode and controls the short-circuit starttime and short-circuit time of a short-circuit element by open-loopcontrol so as to realize the functions to improve the power factor andto boost the voltage. That is, according to the conventional techniqueby Patent Literature 1, a rectifying circuit is controlled to go intothe full-wave rectification mode or the double-voltage rectificationmode by turning on and off a switch for switching the rectifyingcircuit, and therefore the direct-current output voltage range of thepower-factor improving circuit is divided broadly into two levels; andthe divided area of each of the two levels is further divided byopen-loop variable short control of the short-circuit element into twolevels, one without an improved power factor and one with an improvedpower factor, for a total of four levels of direct-current outputvoltage areas; so that the power factor on the high-load side can beimproved with the output range of the direct-current output voltagebeing extended.

According to the conventional technique described in Patent Literature 2below, provided is a direct-current voltage control unit that outputs adirect-current voltage control signal corresponding to the deviationvalue between a direct-current output voltage reference value setcorresponding to the load and the voltage across the terminals of asmoothing capacitor; and also provided is a current reference arithmeticunit that outputs a current reference signal on the basis of the productof the control signal from the direct-current voltage control unit and asinusoidal synchronizing signal synchronous with an alternating-currentpower supply. By comparing this current reference signal and the currenton the alternating-current side of a rectifying element, a switchelement is on/off-controlled at a high frequency, and thereby thedirect-current output voltage is controlled to be at a desired valuewhile the alternating-current input current is controlled to besinusoidal. Therefore the occurrence of harmonics can be suppressed withthe source power factor being at one.

CITATION LIST Patent Literature

Patent Literature 1: Japanese Patent Application Laid-open PublicationNo. H11-206130

Patent Literature 2: Japanese Patent description No. 2140103

SUMMARY Technical Problem

However, according to the conventional techniques by the above PatentLiteratures 1, 2, the control pattern of the short-circuit element islimited. That is, according to these conventional techniques, thecontrol pattern of the short-circuit element is limited to either ahigh-frequency switching mode in which the current is fed back acrossthe entire load area or a partial switching mode of current open-loopcontrol. Thus, according to these conventional techniques, in the lowload area, the short-circuit element is made not to operate in order toavoid the direct-current output voltage excessively rising, and thus thepower factor improvement is not performed. Therefore, in the low loadarea, the waveform distortion of the input current is large so that acurrent containing harmonic components in large amounts flows through areactor; and thus reactor iron loss increases, resulting in a decreasein the AC/DC conversion efficiency of the power-factor improvingcircuit.

Further, in the conventional technique by the above Patent Literature 1,the short-circuit control of the short-circuit element when thepower-factor improvement is performed is made in a partial switchingmethod that controls the short-circuit start time and short-circuit timeby the open-loop control to perform short-circuit operation during onlya certain section of the power-supply cycle, and hence, although thepower factor improvement and the boosting of the direct-current outputvoltage are possible; the effect is small on the high-load side wherethe occurrence amount of harmonics is large. Therefore, because theregulations to harmonics will become stricter in the future, a reactorhaving a large inductance value is needed in order to obtain an enoughpower-factor improvement effect, i.e., enough capability of suppressingharmonics with the conventional technique; and thus the problems occursuch as a decrease in the AC/DC conversion efficiency, the circuit sizebecoming larger, and an increase in cost. Further, in a case where thedirect-current output voltage is boosted with suppressing the occurrenceamount of harmonics to a certain level, the boost capability is limited,and thus operation on the high-load side becomes unstable, or the rangeof load selection becomes narrower when taking into considerations ofstable operations on the high-load side.

The present invention was made in view of the above facts, and anobjective thereof is to provide a power converting device that cansatisfy high boost performance and a harmonic standard while achievinghigher efficiency across the entire load operation area.

Solution to Problem

In order to solve the problem and achieve the objective mentioned above,the present invention relates to a power converting device thatincludes: a rectifier circuit that converts alternating-current powerfrom an alternating-current power supply into direct-current power; ashort-circuit unit that short-circuits the alternating-current powersupply via a reactor connected between the alternating-current powersupply and the rectifier circuit; and a control unit that controls anON/OFF operation of the short-circuit unit during a half cycle of thealternating-current power supply. The control unit includes: adriving-signal generating unit that generates a driving signal that is aswitching pulse for controlling the ON/OFF operation of theshort-circuit unit; and a pulse dividing unit that divides the drivingsignal into a plurality of switching pulses.

Advantageous Effects of Invention

The power converting device according to the present invention has theeffect of being able to satisfy high boost performance and a harmonicstandard while achieving higher efficiency over the entire loadoperation area.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram illustrating an example configuration of a powerconverting device according to an embodiment of the present invention.

FIG. 2 is a first configuration diagram illustrating a reference-voltagegenerating circuit used in pulse control.

FIG. 3 is a second configuration diagram illustrating thereference-voltage generating circuit used in pulse control.

FIG. 4 is a diagram illustrating an example configuration of a secondpulse dividing unit.

FIG. 5 is a diagram illustrating a simplified circuit comprising areactor, a short-circuit unit, a rectifying circuit, and a smoothingcapacitor.

FIG. 6 is a diagram illustrating the waveform of the power supplycurrent when a short-circuit element is switched once during apositive-polarity-side half cycle of an AC power supply while in apartial switching pulse mode.

FIG. 7 is a diagram illustrating the waveform of the power supplycurrent in a case where a driving signal is not divided into multiplepulses.

FIG. 8 is a diagram illustrating the waveform of the power supplycurrent in a case where the driving signal is divided into multiplepulses.

FIG. 9 is a diagram illustrating the waveform of the power supplycurrent when the driving signal is divided into multiple pulses duringthe positive-polarity-side half cycle and negative-polarity-side halfcycle.

FIG. 10 is a diagram illustrating the driving signal that switches theshort-circuit unit once during a power-supply half cycle.

FIG. 11 is a diagram illustrating the driving signal that switches theshort-circuit unit multiple times during a power-supply half cycle.

FIG. 12 is a flow chart illustrating a procedure for creating data to beused in a first pulse dividing unit.

FIG. 13 is a diagram illustrating the ON time of the driving signalgenerated by a driving-signal generating unit and also illustrating theON times and OFF times of driving signals divided by the second pulsedividing unit.

FIG. 14 is a graph illustrating changes over time in the ON duty for Ndriving signals generated during the power-supply half cycle.

FIG. 15 is a graph illustrating changes over time in the OFF duty for Ndriving signals generated during the power-supply half cycle.

FIG. 16 is a diagram illustrating a first modified example of the powerconverting device according to the embodiment of the present invention.

FIG. 17 is a diagram illustrating a second modified example of the powerconverting device according to the embodiment of the present invention.

DESCRIPTION OF EMBODIMENTS

A power converting device according to an embodiment of the presentinvention is described in detail below with reference to the drawings.Note that this embodiment is not intended to limit the presentinvention.

Embodiment

FIG. 1 is a diagram illustrating an example configuration of a powerconverting device 100 according to the embodiment of the presentinvention. The device 100 includes a rectifying circuit 3 that convertsAC power from an AC power supply 1 into DC power; a reactor 2 connectedbetween the AC power supply 1 and the rectifying circuit 3; a currentdetecting means 9 that detects the power supply current Is of the ACpower supply 1; a smoothing capacitor 4 connected between the outputends of the rectifying circuit 3 and that smooths the voltage of thefull-wave rectified waveform output from the rectifying circuit 3; a DCvoltage detector 5 that detects the DC output voltage Vdc that is thevoltage across the smoothing capacitor 4; a power supply voltagedetector 6 that detects the power supply voltage Vs of the AC powersupply 1; a short-circuit unit 30 that short-circuits the AC powersupply 1 via the reactor 2; and a control unit 20 that generates drivingsignals Sa2, which are multiple switching pulses, during the half cycleof the AC power supply 1 and that controls the opening and closing ofthe short-circuit unit 30 with the generated driving signals Sa2.

The reactor 2 is connected on the AC power supply 1 side of theshort-circuit unit 30 and is inserted between one input end of therectifying circuit 3 and the AC power supply 1. The rectifying circuit 3includes a diode bridge in which four diodes are combined. Not beinglimited to this, the rectifying circuit 3 can include a combination ofdiode-connected metal oxide film semiconductor field-effect transistorsthat are unidirectional conductive elements.

The DC voltage detector 5 includes an amplifier or a level shiftcircuit, and it detects the voltage across the smoothing capacitor 4;converts the detected voltage into the DC output voltage Vdc, which is adetected voltage value within voltage range low enough for the controlunit 20 to handle; and outputs the DC output voltage Vdc.

The current detecting means 9 includes a current detecting element 8 anda current detector 7. The current detecting element 8 is connectedbetween the reactor 2 and the rectifying circuit 3 in order to detectthe current value at the connection position. A current transformer or ashunt resistor is, for example, used as the current detecting element 8.The current detector 7 includes an amplifier or a level shift circuitand it converts a voltage proportional to the current detected by thecurrent detecting element 8 into a current detection voltage Vis, whichis within voltage range low enough for the control unit 20 to handle;and outputs the current detection voltage Vis.

The short-circuit unit 30, which is a bidirectional switch, includes adiode bridge 31 connected in parallel with the AC power supply 1 via thereactor 2 and a short-circuit element with ends that are connected toopposite output ends of the diode bridge 31. If the short-circuitelement 32 is a metal oxide film semiconductor field-effect transistor,the gate of the short-circuit element 32 is connected to a pulsetransmission unit 22; and the short-circuit element 32 is turned on/offby a driving signal Sa2 from the pulse transmission unit 22. When theshort-circuit element 32 is turned on, the AC power supply 1 isshort-circuited via the reactor 2 and the diode bridge 31.

The control unit 20 includes a microcomputer and includes adriving-signal generating unit 21 that generates a driving signal Sa,which is a switching pulse, to control the short-circuit element 32 ofthe short-circuit unit 30 and a reference voltage V_(ref) on the basisof the DC output voltage Vdc and the power supply voltage Vs; a pulsedividing unit 23 that divides the driving signal Sa from thedriving-signal generating unit 21 into multiple pulses to be output asthe driving signals Sa1, which are multiple divided pulses, to the pulsetransmission unit 22; and the pulse transmission unit 22 that convertsthe driving signals Sa1 from the pulse dividing unit 23 into drivingsignals Sa2 to transmit to the short-circuit unit 30.

The reference voltage V_(ref) is a hysteresis reference voltage, whichis a threshold to limit the value of the power supply current Is. Thereference voltage V_(ref) is a positive-polarity-side reference voltageV_(refH) and a negative-polarity-side reference voltage V_(refL). Acircuit that generates the reference voltage V_(ref) is described later.

The pulse dividing unit 23 includes a first pulse dividing unit 23 athat divides the driving signal Sa into driving signals Sa1, which aremultiple pulses, by performing processing using software; a second pulsedividing unit 23 b that divides the driving signal Sa into multipledriving signals Sa1 by hardware processing; a data storage unit 23 cthat stores data necessary for performing calculation in the first pulsedividing unit 23 a; and a selector 23 d that selects the driving signalsSa1 from the first pulse dividing unit 23 a or the driving signals Sa1from the second pulse dividing unit 23 b so as to output them to thepulse transmission unit 22. The details of the first pulse dividing unit23 a and second pulse dividing unit 23 b are described later.

The selector 23 d has two terminals on the input side. When its internalcontact point is connected to the X-side terminal, the driving signalsSa1 generated by the first pulse dividing unit 23 a are output to thepulse transmission unit 22; and when the internal contact point isconnected to the Y-side terminal, the driving signals Sa1 generated bythe second pulse dividing unit 23 b are output to the pulse transmissionunit 22.

The pulse transmission unit 22 includes a level shift circuit, and itperforms a voltage-level shift so as to be able to perform gate driving;and converts the driving signals Sa1 from the pulse dividing unit 23into the driving signals Sa2, which are gate driving signals, to beoutput to the short-circuit unit 30.

FIG. 2 is a first configuration diagram illustrating a reference-voltagegenerating circuit used in pulse control; and FIG. 3 is a secondconfiguration diagram illustrating the reference-voltage generatingcircuit used in pulse control. The circuit illustrated in FIG. 2converts a pulse width modulation signal that is a port output Sb of thedriving-signal generating unit 21 into a DC value by using a low-passfilter, thereby generating the reference voltage V_(ref). In this case,by controlling the duty ratio of the pulse width modulation signal, thevalue of the reference voltage V_(ref) can be changed seamlessly. Thecircuit illustrated in FIG. 3 changes the value of the reference voltageV_(ref) stepwise according to the voltage division ratio of theresistances Rb and Rc by driving a switch TR in accordance with the portoutput Sb of the driving-signal generating unit 21. The circuit thatgenerates the reference voltage V_(ref), not being limited to thecircuits illustrated in FIGS. 2, 3, can be a known circuit other thanthe circuits illustrated in FIGS. 2, 3. Further, a reference voltageV_(ref) that is generated outside the control unit 20 can be used.

FIG. 4 is a diagram illustrating an example configuration of the secondpulse dividing unit 23 b. The second pulse dividing unit 23 b has apositive-polarity-side hysteresis comparator HCH that determines, forhysteresis corresponding to the current control range on thepositive-polarity side, by the relation between thepositive-polarity-side upper-limit threshold calculated using theequation (1), the positive-polarity-side lower-limit thresholdcalculated using the equation (2), and the positive-polarity-sidereference voltage V_(refH), and that controls the waveform of thecurrent detection voltage Vis; and a negative-polarity-side hysteresiscomparator HCL that determines, for hysteresis corresponding to thecurrent control range on the negative-polarity side, by the relationbetween the negative-polarity-side upper-limit threshold calculated fromthe equation (1), the negative-polarity-side lower-limit thresholdcalculated from the equation (2), and the negative-polarity-sidereference voltage V_(refL), and that controls the waveform of thecurrent detection voltage Vis. Further, the second pulse dividing unit23 b includes a NOT logic IC 3 that inverts the output of thepositive-polarity-side hysteresis comparator HCH; an AND logic IC 2′that performs an AND-gate logic on the output of the NOT logic IC 3 andthe driving signal Sa so as to output a positive-polarity-side drivingsignal SaH; an AND logic IC 2 that performs an AND-gate logic on theoutput of the negative-polarity-side hysteresis comparator HCL and thedriving signal Sa so as to output a negative-polarity-side drivingsignal SaL; and an AND logic IC 4 that performs an AND-gate logic on thepositive-polarity-side driving signal SaH and the negative-polarity-sidedriving signal SaL so as to output the driving signal Sa1 that is theresult of performing the AND logic. The current control range is thetarget control range of the power supply current Is of the AC powersupply 1: the upper-limit threshold regulates the upper limit of theshort-circuit current that flows when the short-circuit unit 30 is on;and the lower-limit threshold is set to a smaller value than theupper-limit threshold. V_(d) in the equation (1) denotes alow-voltage-system power supply; and V_(OL) in the equation (2) denotesthe output saturation voltage of an operational amplifier.

$\begin{matrix}\left\lbrack {{Formula}\mspace{14mu} 1} \right\rbrack & \; \\{{V_{THH}(H)} = {V_{refH} + {\frac{R_{1}}{R_{1} + R_{2} + R_{3}}\left( {V_{d} - V_{refH}} \right)}}} & (1) \\\left\lbrack {{Formula}\mspace{14mu} 2} \right\rbrack & \; \\{{V_{THH}(L)} = {V_{refH} + {\frac{R_{1}}{R_{1} + R_{2} + R_{3}}\left( {V_{refH} - V_{OL}} \right)}}} & (2)\end{matrix}$

The current detector 7 illustrated in FIG. 1 has a level shift circuitand an amplifier provided at the output stage of the current detectingelement 8 and it converts the current waveform of an alternating currentdetected by the current detecting element 8, with half of thelow-voltage-system power supply Vd corresponding to 0 amperes, into acurrent waveform having only the positive side to output. Thus, thesecond pulse dividing unit 23 b can generate the driving signals Sa1regardless of current polarity.

By using the second pulse dividing unit 23 b with a configuration thatincludes the plurality of hysteresis comparators, the driving signalsSa1 can be generated regardless of current polarity. By controlling thewaveform of the power supply current Is, i.e., the current detectionvoltage Vis, by using the driving signals Sa1, the DC output voltage Vdccan be boosted while suppressing the peak values of the short-circuitcurrent flowing when the short-circuit unit 30 is turned on.

In the hysteresis comparators, the widths of the hysteresis can bechanged by changing the resistance values of the resistors R1, R1′, R2,R2′, R3, and R3′. For example, if a series circuit made up of a switchand a resistor is connected in parallel with the resistor R2 or R2′, thecombined resistance value can be changed by opening and closing theswitch. By making the hysteresis comparators perform part of theprocessing load of the control unit 20, the calculation load on thecontrol unit 20 is reduced so that the power converting device 100 canbe made of an inexpensive central processing unit.

The operation is described below. FIG. 5 is a diagram illustrating asimplified circuit comprising a reactor 2, a short-circuit unit 30, arectifying circuit 3, and a smoothing capacitor 4. FIG. 5 alsoillustrates current paths when the short-circuit unit 30 is turned onand off. FIG. 6 is a diagram illustrating the waveform of the powersupply current Is when the short-circuit element is switched once duringa positive-polarity-side half cycle of the AC power supply 1 when in apartial switching pulse mode. FIG. 6 illustrates the driving signal Sa1as a single pulse in the example operation performed while in thepartial switching pulse mode, which is where the short-circuit unit 30is switched once during a power-supply half cycle. The partial switchingpulse mode is a mode in which the short-circuit unit 30 is turned on/offonce or multiple times, i.e., a short-circuit operation is performedonce or multiple times during a power-supply half cycle while undercurrent open-loop control. When in the partial switching pulse mode, bycontrolling the short-circuit start time and short-circuit duration timeof the short-circuit unit 30, the energy stored in the reactor 2 can becontrolled so that the DC output voltage Vdc can be boosted in astepless manner. Although FIG. 6 illustrates the driving signal Sa1 as asingle pulse in a case where the short-circuit unit 30 is turned on/offonce during a power-supply half cycle, the number of times when theshort-circuit unit 30 is switched during a power-supply half cycle canbe two or greater.

When the short-circuit unit 30 is turned on, a closed circuit is formedby the AC power supply 1, the reactor 2, and the short-circuit unit 30so that the AC power supply 1 is short-circuited via the reactor 2.Hence, the power supply current Is flows through the closed circuit; andmagnetic energy, obtained by dividing the square of the value I of powersupply current Is multiplied by the inductance L of reactor 2 by two, isstored in the reactor 2. At the same time when the short-circuit unit 30is turned off, the stored energy is discharged into the load 10 side tobe rectified by the rectifying circuit 3 and transferred to thesmoothing capacitor 4. By following this series of operations, the powersupply current Is flows along the current path in FIG. 5. Thus, thecurrent-carrying angle of the power supply current Is can be extendedwhen compared with a passive mode without an improvement in the powerfactor, with the extension of the current carrying angle resulting in animprovement in the power factor.

FIG. 7 illustrates the waveform of the power supply current Is when thedriving signal Sa is not being divided into multiple pulses. At the timewhen the driving signal Sa is turned on, the driving signal Sa1 isturned on; and the driving signal Sa1 is also on for a length of timeequal to the ON period t during the ON period t of the driving signalSa. The ON period t is a period from when the driving signal Sa isturned on to when it is turned off. Thus, the short-circuit time of theshort-circuit element 32 becomes longer in proportion to the ON period tof the driving signal Sa when the power supply voltage Vs is boosted,and thus the power supply current Is increases. When the power supplycurrent Is reaches a set value, the driving signal Sa is turned off, andat the time when the driving signal Sa is turned off, the driving signalSa1 is turned off.

If the short-circuit time period of the short-circuit element 32 isextended, more energy can be stored in the reactor 2; but problems occurin that the power factor becomes worse, that the number of harmoniccomponents increases, and that circuit loss increases because the peakof the power supply current Is becomes larger.

FIG. 8 illustrates the waveform of the power supply current Is when thedriving signal Sa is divided into multiple pulses. At the time when thedriving signal Sa is turned on, the driving signal Sa1 is turned on, andthe power supply current Is increases. As the power supply current Isincreases, the current detection voltage Vis, i.e., the current valuedetected by the current detector 7, goes up. When the detected currentvalue becomes greater than the upper-limit threshold while the drivingsignal Sa is on, the pulse dividing unit 23 turns off the driving signalSa1. Thus, the power supply current Is decreases, and therefore thedetected current value goes down. Then, when the detected current valuebecomes less than the lower-limit threshold while the driving signal Sais on, the pulse dividing unit 23 turns on the driving signal Sa1 again.Thus, the power supply current Is increases again, and therefore thecurrent value detected by the current detector 7 goes up.

The driving signal Sa1 is repeatedly switched on/off during the ONperiod t of the driving signal Sa, and thus the peak values of thecurrent detection voltage Vis, i.e., the peak values of the power supplycurrent Is, are controlled such that they are within the current controlrange w during the ON period t of the driving signal Sa. Thus, even whenthe DC output voltage Vdc is boosted to a relatively high value, thepeak values of the power supply current Is during the ON period t of thedriving signal Sa are suppressed more than the peak value when thedriving signal Sa1 changes from on to off.

By adjusting the upper-limit and lower-limit thresholds of the currentcontrol range w, the number of times the driving signal Sa1 is switched,i.e., the switching frequency of the driving signal Sa1 during the ONperiod t of the driving signal Sa, can be controlled.

FIG. 9 is a diagram illustrating the waveform of the power supplycurrent when the driving signal Sa is divided into multiple pulsesduring the positive-polarity-side half cycle and negative-polarity-sidehalf cycle. FIG. 9 illustrates a positive-polarity-side driving signalSaH, a negative-polarity-side driving signal SaL, apositive-polarity-side upper-limit threshold V_(THH)(H), apositive-polarity-side lower-limit threshold V_(THH)(L), anegative-polarity-side upper-limit threshold V_(THL)(H), and anegative-polarity-side lower-limit threshold V_(THL)(L) when the secondpulse dividing unit 23 b performs division.

Because the operation of dividing into pulses is performed for thepositive and negative polarity sides of the AC power supply 1, the peakvalues of the power supply current Is on the positive-polarity side arewithin a current control range w with the positive-polarity-sidereference voltage V_(refH) as the center value; and the peak values ofthe power supply current Is on the negative-polarity side are within acurrent control range w with the negative-polarity-side referencevoltage V_(refL) as the center value.

If the switching frequency is relatively high, the switching causes theproblems of increase in loss, radiant noise, and noise terminal voltage.In solving these problems, by extending the current control range w withthe reference voltage V_(ref) as the center value, the number ofswitching times of the driving signal Sa1 is reduced. Thus, theswitching frequency is lowered so that the increase in loss, radiantnoise, and noise terminal voltage can be suppressed.

In contrast, when the switching frequency is relatively low, the problemof noise in an audible frequency band can occur. In solving thisproblem, by narrowing the current control range w with the referencevoltage V_(ref) as the center value, the number of switching times ofthe driving signal Sa1 is increased. Thus, the switching frequency israised so that the noise can be suppressed.

Next, the configuration of the first pulse dividing unit 23 a isdescribed. When the short-circuit unit 30 is switched using the firstpulse dividing unit 23 a, the ON and OFF timings of the short-circuitunit 30 need to be determined. To this end, the rise time Ta and falltime Tb of the driving signal Sa need to be identified.

FIG. 10 is a diagram illustrating the driving signal that switches theshort-circuit unit 30 once during a power-supply half cycle; FIG. 11 isa diagram illustrating the driving signal that switches theshort-circuit unit 30 multiple times during a power-supply half cycle.

Given that T1 a and T1 b be the times when the driving signal Sa risesand falls at time points when a certain time has elapsed from a zerocross point T0 respectively. For example, if the time from the zerocross point T0 to T1 a and the time from the zero cross point T0 to T1 bare held as data, the ON and OFF times of the short-circuit unit 30 canbe identified. By using these time data, the first pulse dividing unit23 a can switch the short-circuit unit 30 once during a power-supplyhalf cycle as illustrated in FIG. 10.

In contrast, when the short-circuit unit 30 is switched N number oftimes during a power-supply half cycle, N is an integer of two orgreater, as illustrated in FIG. 11. Given Tna and Tnb be the times whenan nth driving signal Sa rises and falls at time points when a certaintime has elapsed from a zero cross point T0 respectively. In this case,a number of data proportional to the value of n need to be held toidentify the ON and OFF timings of the short-circuit unit 30; and thuscontrol parameters increase in number as the number of switching timesincreases. The designing the control parameters can become complexdepending on operation conditions such as a DC voltage instruction, thesize of the load, and the type of the load; and thus the increase in thenumber of switching times results in a lot of time consumptions in thereliability verification or evaluation of the data.

In contrast, when the second pulse dividing unit 23 b constituted byhardware is used, reliability verification or evaluation of data isunnecessary. But, for example, if the hardware configuration needs to bechanged to make adaptable to operation conditions, it can be difficultto change the configuration because of constraints of size or cost.

The inventors of the present patent application directed their attentionto tendencies of changes over time in the ON times and OFF times ofmultiple driving signals Sa1 generated during the power-supply halfcycle so that the peak values of the power supply current Is are withinthe current control range w and have come up with the highly-reliablepower converting device 100 that suppresses increase in controlparameters, thus reducing the time and load required for reliabilityverification or evaluation so as to achieve higher efficiency withoutcausing a large increase in cost.

FIG. 12 is a flow chart illustrating a procedure of creating data to beused in the first pulse dividing unit 23 a. An example is described in acase where data to be stored into the data storage unit 23 c is obtainedusing multiple driving signals Sa1 generated by the second pulsedividing unit 23 b illustrated in FIG. 1.

(Step S1)

The internal contact point of the selector 23 d illustrated in FIG. 1 isswitched to the Y-side terminal. By this operation, driving signals Sa1can be automatically obtained using the driving signal Sa generated bythe driving-signal generating unit 21.

(Step S2)

Operation conditions are set in, e.g., the driving-signal generatingunit 21.

(Step S3)

A current limiting level and the current control range w for the powersupply current Is are adjusted. The current limiting level is determinedby the positive-polarity-side reference voltage V_(refH) and thenegative-polarity-side reference voltage V_(refL); and the currentcontrol range w is determined by the resistance values of the resistorsR1, R1′, R2, R2′, R3, and R3′ illustrated in FIG. 4. The currentlimiting level and the current control range w are adjusted using theselimited parameters so that desired performance of boosting, power-supplypower factor, or harmonic current can be obtained.

(Step S4)

The rise time and fall time of the driving signal Sa generated by thedriving-signal generating unit 21 under the operation conditions set atstep S2 and with the parameters adjusted at step S3 are collected; andthe rise times and fall times of multiple driving signals Sa1 generatedby the second pulse dividing unit 23 b using the parameters of step S3are collected. The data collection is by the analysis or the use of anactual device.

(Step S5)

The ON time Ton of the driving signal Sa and the ON time Ton and OFFtime Toff of each driving signal Sa1 are determined using data collectedat step S4.

FIG. 13 is a diagram illustrating the ON time Ton of the driving signalSa generated by the driving-signal generating unit 21 and the ON timesTon and OFF times Toff of driving signals Sa1 divided by the secondpulse dividing unit 23 b.

FIG. 13 illustrates the driving signal Sa generated during thepositive-polarity-side half cycle and negative-polarity-side half cycleof the power supply voltage Vs, and N number of driving signals Sa1generated during the ON time Ton of the driving signal Sa, where N is aninteger of two or greater.

When a certain time Td1 has elapsed from a zero cross point T0 duringthe rise of the power supply voltage Vs, the driving signal Sa and thefirst driving signal Sa1 both become on. Ton(1) denotes the ON time ofthe first driving signal Sa1 generated during the positive-polarity-sidehalf cycle, i.e., the time from when the first driving signal Sa1 risesto the time when it falls. Ton(2) denotes the ON time of the seconddriving signal Sa1 generated during the positive-polarity-side halfcycle; and Ton(N) denotes the ON time of the Nth driving signal Sa1generated during the positive-polarity-side half cycle.

Likewise, when a certain time has elapsed from a zero cross point duringthe fall of the power supply voltage Vs, the driving signal Sa and thefirst driving signal Sa1 both become on. Toff(1) denotes the OFF timebetween the first driving signal Sa1 and the second driving signal Sa1generated during the negative-polarity-side half cycle, i.e., the timefrom when the first driving signal Sa1 falls to the time when the seconddriving signal Sa1 rises. Toff(2) denotes the OFF time between thesecond driving signal Sa1 and the third driving signal Sa1 generatedduring the negative-polarity-side half cycle; and Toff(N−1) denotes theOFF time between the (N−1)th driving signal Sa1 and the Nth drivingsignal Sa1 generated during the negative-polarity-side half cycle.

The ON time Ton of the driving signal Sa and the ON time Ton and OFFtime Toff of each driving signal Sa1 illustrated in FIG. 13 are obtainedaccording to the rise time and fall time of the driving signal Sa andthe rise times and fall times of the first to Nth individual drivingsignals Sa1 collected at step S4. Further, the pulse number of eachdriving signal Sa1 and the inter-pulse number of the interval betweenthe driving signal Sa1 and the next driving signal Sa1 are obtainedaccording to the order of the driving signals Sa1 collected.

(Step S6)

Next, the ON duty of the ON time Ton of each driving signal Sa1 for theON time Ton of the driving signal Sa and the OFF duty of the OFF timeToff of each driving signal Sa1 for the ON time Ton of the drivingsignal Sa are obtained by using the ON time and OFF time of each drivingsignal Sa1 obtained at step S5.

As mentioned above, when directing attention to tendencies of changesover time in the ON times and OFF times of multiple driving signals Sa1generated during the power-supply half cycle, one can find regularity inthe ON duties and the OFF duties. A specific description is made below.

The following functions are defined so as to calculate the ON duty andthe OFF duty.

$\begin{matrix}\left\lbrack {{Formula}\mspace{14mu} 3} \right\rbrack & \; \\{{{on\_ duty}(x)} = {\frac{T_{on}(x)}{T_{on}}\mspace{14mu}\left\{ {2 \leq x \leq N} \right\}}} & (3) \\\left\lbrack {{Formula}\mspace{14mu} 4} \right\rbrack & \; \\{{{off\_ duty}(y)} = {\frac{T_{off}(y)}{T_{on}}\mspace{14mu}\left\{ {1 \leq y \leq \left( {N - 1} \right)} \right\}}} & (4)\end{matrix}$

The equation (3) expresses the ON duty of the ON time Ton(x) of the xthdriving signal Sa1 in the power-supply half cycle for the ON time Ton ofthe driving signal Sa. N is the total number of driving signals Sa1generated during the power-supply half cycle.

The equation (4) expresses the OFF duty of the OFF time Toff(y) betweenthe xth driving signal Sa1 and the (x−1)th driving signal Sa1 in thepower-supply half cycle for the ON time Ton of the driving signal Sa. Nis the total number of driving signals Sa1 generated during thepower-supply half cycle.

FIG. 14 is a graph illustrating changes over time in the ON duty for Ndriving signals Sa1 generated during the power-supply half cycle. Thehorizontal axis represents the pulse number x, which takes on numbers ofsecond to Nth ones of N driving signals Sa1 generated during thepower-supply half cycle, and the vertical axis represents the ON dutyfor the second to Nth driving signals Sa1 n obtained from the equation(3).

Paying attention to a pulse train of the second to Nth driving signalsSa1, it is understood that the ON duty, when the peak values of thepower supply current Is are within the current control range w asillustrated in FIG. 9, draws a parabola pointing downward and has acharacteristic illustrating relatively gentle gradients.

FIG. 15 is a graph illustrating changes over time in the OFF duty for Ndriving signals Sa1 generated during the power-supply half cycle. Thehorizontal axis represents the inter-pulse number y, which is the numberof the interval between each driving signal Sa1 and the next generatedduring the power-supply half cycle, and the vertical axis represents theOFF duty for the first to Nth driving signals Sa1 n obtained from theequation (4).

Paying attention to a pulse train of the first to Nth driving signalsSa1, it is seen that the OFF duty, when the peak values of the powersupply current Is are within the current control range w as illustratedin FIG. 9, draws a parabola pointing upward and has a characteristicillustrating steeper gradients than the ON duty.

(Step S7)

The ON duty and OFF duty for multiple driving signals Sa1 generatedduring the power-supply half cycle change over time and are different inthe tendency of change. The inventors of the present patent applicationcame up with a method of expressing the ON duty and OFF duty for drivingsignals Sa1 in a particular area from among multiple driving signals Sa1generated during the power-supply half cycle as approximate expressions.

The ON duty has a characteristic illustrating relatively gentlegradient. Hence, the ON duty given by the equation (3) can beapproximated by, e.g., a quadratic expressed by the equation (5), whereA₁, B₁, and C₁ are constants of the approximate expression.[Formula 5]on_duty(x)=A ₁ ·x ² +B ₁ ·x+C ₁{2≤x≤N}  (5)

Although the OFF duty given by the equation (4) can be approximated by aquadratic, the OFF duty has a characteristic illustrating relativelysteep gradients as compared with the ON duty. In the present embodiment,in order to increase the degrees of freedom in duty setting, it isapproximated by a biquadratic expressed by the equation (6), where A₂,B₂, C₂, D₂, and E₂ are constants of the approximate expression.[Formula 6]off_duty(y)=A ₂ ·y ⁴ +B ₂ ·y ₃ +C ₂ ·y ² +D ₂ ·y+E ₂{1≤y≤(N−1)}  (6)

The ON duty of the first driving signal Sa1, which is a pulse in an areaother than the particular area, can be expressed by the equation (7). Nis the total number of driving signals Sa1 generated during thepower-supply half cycle. As such, for the ON time of the first drivingsignal Sa1, an error associated with the approximate expression can beabsorbed by using the equation (7) without setting the ON duty.

$\begin{matrix}\left\lbrack {{Formula}\mspace{14mu} 7} \right\rbrack & \; \\{{{on\_ duty}(1)} = {1 - {\sum\limits_{k = 2}^{N}{{on\_ duty}(k)}} - {\sum\limits_{k = 1}^{N - 1}{{off\_ duty}(k)}}}} & (7)\end{matrix}$

In this way, an approximate expression of the ON duty for drivingsignals Sa1 in the particular area from among multiple driving signalsSa1 generated during the power-supply half cycle, an approximateexpression of the OFF duty for multiple driving signals Sa1 generatedduring the power-supply half cycle, and the ON duty of a driving signalSa1 in an area other than the particular area are obtained.

(Step S8)

The ON duties obtained at step S7 are associated with pulse numbers soas to form a function; the OFF duties obtained at step S7 andinter-pulse numbers are made to form a function; and these data in theform of functions and data about constants of the approximateexpressions are stored into the data storage unit 23 c.

The first pulse dividing unit 23 a measures the ON time Ton of thedriving signal Sa from the driving-signal generating unit 21 andmultiplies the ON duty and OFF duty read from the data storage unit 23 cby the ON time Ton of the driving signal Sa, thereby determining the ONand OFF times of the first to Nth driving signals Sa1 in thepower-supply half cycle. Thus, the ON and OFF timings of theshort-circuit unit 30 are uniquely determined so that, at these ON andOFF timings, the driving signal Sa can be divided into multiple drivingsignals Sa1.

As such, by using functions expressing the pulse train arrangement interms of duties, the ON and OFF timings of the short-circuit unit 30 canbe identified without causing an increase in the number of controlparameters to be stored into the data storage unit 23 c when the numberof switching times increases.

Note that although in the present embodiment the reactor 2 is insertedbetween the AC power supply 1 and the rectifying circuit 3, and therectifying circuit 3 is connected to the AC power supply 1 via thereactor 2, the positional relation between the rectifying circuit 3, thereactor 2, and the short-circuit unit 30 is not limited to the exampleconfiguration illustrated in the figure because the highly-reliablepower converting device 100 need only be able to short-circuit and openthe power supply via the reactor 2. That is, the highly-reliable powerconverting device 100 need only be configured such that the power supplycurrent Is flows through the AC power supply 1, the reactor 2, theshort-circuit unit 30, and the AC power supply 1 in that order at thetime of short-circuiting; and it can have, e.g., a configuration wherethe rectifying circuit 3 is inserted between the AC power supply 1 andthe reactor 2, in which the reactor 2 is connected to the AC powersupply 1 via the rectifying circuit 3.

Although in the present embodiment the power supply voltage Vs, thepower supply current Is, and the DC output voltage Vdc are detected togenerate the driving signals Sa1, the power supply current Is does notnecessarily need to be detected while the first pulse dividing unit 23 ais made to operate according to data stored in the data storage unit 23c, but it should be selected depending on the system specification to beconstructed whether the power supply current detection is needed.Although the present embodiment describes an example where the dutiesare expressed by functions, data in the form of functions expressing ONtimes and OFF times or data in the form of quadratic or higher-degreeapproximate expressions expressing ON times and OFF times can be storedinto the data storage unit 23 c to be used in pulse dividing operation.

Although the present embodiment describes an example where pulses aregenerated using approximate expressions, for example, if the number ofdriving signals Sa1 generated during the power-supply half cycle isrelatively small, the control unit 20 can be configured such that withdata about duties obtained at step S6 being stored instead ofapproximate expressions or data about the ON time of each pulse and theOFF time between each pulse and the next obtained at step S5 beingstored, and thus driving signals Sa1 are generated using these data.Also with this configuration, the first pulse dividing unit 23 a canperform pulse division so that an increase in cost associated withimprovement in the control unit 20 can be reduced.

Only one of the first pulse dividing unit 23 a and the second pulsedividing unit 23 b can be used, or they can be changed from one to theother to be used according to operation conditions. For example, if itis difficult to change the configuration of the control unit 20 becauseof constraints of size or cost, only the first pulse dividing unit 23 ais used with the internal contact point of the selector 23 d beingconnected to the X-side terminal. If, although constraints of cost arenot serious, accuracy in generating the waveform of the power supplycurrent Is needs to be raised in order to use it in variousspecification environments, only the second pulse dividing unit 23 b isused with the internal contact point of the selector 23 d beingconnected to the Y-side terminal. If a particular pulse pattern needs tobe output without depending on the power supply current Is for noisecontrol under particular operation conditions while raising accuracy ingenerating the waveform, the internal contact point of the selector 23 dis switched to the X-side terminal or the Y-side terminal according tooperation conditions, and thus both the first pulse dividing unit 23 aand the second pulse dividing unit 23 b are used.

Although the present embodiment has described an example operationwhere, with making the value of the reference voltage V_(ref) constant,the power supply current Is in a rectangular wave shape is generated,the device 100 can be configure such that, with making the referencevoltage V_(ref) change over time, the power supply current Is in a shapeother than the rectangular wave is generated. Although the presentembodiment has described an example where data to be stored into thedata storage unit 23 c is obtained using driving signals Sa1 generatedby the second pulse dividing unit 23 b, not being limited to this, inanalysis in advance, a function associating the ON duty of each drivingsignal Sa1 with the pulse number and a function associating the OFF dutyof each driving signal Sa1 with the inter-pulse number are obtained onthe basis of such ON and OFF times of the driving signals Sa1 that thepeak values of the power supply current Is are within the currentcontrol range w during the ON period of the driving signal Sa, and thesedata in the form of functions and data about constants of theapproximate expressions can be stored into the data storage unit 23 c.

Alternatively, the first pulse dividing unit 23 a can have the followingconfiguration. FIG. 16 is a diagram illustrating a first modifiedexample of the power converting device 100 according to the embodimentof the present invention. For simplicity of description, given that datastored in the data storage unit 23 c is ON times and OFF times or ONduties and OFF duties. In the power converting device 100 illustrated inFIG. 16, the current detection voltage Vis detected by the currentdetecting means 9 is input to the first pulse dividing unit 23 a, andthe first pulse dividing unit 23 a calculates correction coefficients tocorrect ON duties and OFF duties or ON times and OFF times on the basisof the current detection voltage Vis. The first pulse dividing unit 23 amultiplies ON duties and OFF duties or ON times and OFF times read fromthe data storage unit 23 c by the correction coefficients. The firstpulse dividing unit 23 a multiplies the corrected ON duties and OFFduties or ON times and OFF times by the ON time Ton of the drivingsignal Sa. With this configuration, accuracy of the ON and OFF times ofthe driving signals Sa1 can be improved.

Alternatively, the pulse dividing unit 23 can have the followingconfiguration. FIG. 17 is a diagram illustrating a second modifiedexample of the power converting device 100 according to the embodimentof the present invention. From the pulse dividing unit 23 illustrated inFIG. 17, the selector 23 d and the second pulse dividing unit 23 billustrated in FIG. 16 are omitted. That is, the pulse dividing unit 23includes the first pulse dividing unit 23 a and the data storage unit 23c; the first pulse dividing unit 23 a calculates correction coefficientsto correct ON times and OFF times on the basis of the current detectionvoltage Vis; and driving signals Sa1 generated by the first pulsedividing unit 23 a are output directly to the pulse transmission unit22. Where ON duties and OFF duties are not corrected, the pulse dividingunit 23 can be configured such that the current detection voltage Vis isnot input to the first pulse dividing unit 23 a. Where correctioncoefficients are not calculated, the pulse dividing unit 23 can beconfigured such that the current detection voltage Vis is not input tothe first pulse dividing unit 23 a.

Note that where only the second pulse dividing unit 23 b is used, thepulse dividing unit 23 can also be configured likewise. In this case,the pulse dividing unit 23 has only the second pulse dividing unit 23 billustrated in FIG. 16, and driving signals Sa1 generated by the secondpulse dividing unit 23 b are output directly to the pulse transmissionunit 22.

As described above, the power converting device 100 according to thepresent embodiment includes the rectifying circuit that converts ACpower from the AC power supply into DC power; the short-circuit unitthat short-circuits the AC power supply via the reactor connectedbetween the AC power supply and the rectifying circuit; and the controlunit that controls the ON and OFF operation of the short-circuit unitduring the half cycle of the AC power supply. The control unit has thedriving-signal generating unit that generates a driving signal that is aswitching pulse to control the ON and OFF operation of the short-circuitunit and the pulse dividing unit that divides the driving signal intomultiple switching pulses. With this configuration, the power convertingdevice 100 that is highly reliable while achieving higher efficiency canbe provided.

The pulse dividing unit divides the driving signal into multipleswitching pulses by either performing processing using software orhardware. With this configuration, if it is difficult to change theconfiguration of the control unit 20 because of constraints of size orcost, pulse division by processing using software can be performed; andif accuracy in generating the waveform of the power supply current Isneeds to be raised in order to use it in various specificationenvironments, pulse division by hardware processing can be performed.

The pulse dividing unit includes the first pulse dividing unit thatdivides the driving signal into multiple switching pulses by processingusing software; the second pulse dividing unit that divides the drivingsignal into multiple switching pulses by hardware processing; and theselector that selects the switching pulses from the first pulse dividingunit or the switching pulses from the second pulse dividing unit tooutput. With this configuration, the first pulse dividing unit 23 a andthe second pulse dividing unit 23 b can be easily switched from one tothe other to be used according to operational conditions.

Further, the pulse dividing unit comprises the data storage unit thatstores data used in dividing the driving signal into multiple switchingpulses by processing using software and divides the driving signal intomultiple switching pulses on the basis of the data stored in the datastorage unit. With this configuration, pulse division can be performedwithout inputting data from the outside of the control unit 20.

Further, data stored in the data storage unit is the number of divisionsof the driving signal and the ON times and OFF times of the multipleswitching pulses; or the number of divisions of the driving signal, ONduties of the ON times of the multiple switching pulses for the ON timeof the driving signal, and OFF duties of the OFF times of the multipleswitching pulses for the ON time of the driving signal. If the number ofdriving signals Sa1 is relatively small, the ON and OFF timings of theshort-circuit unit 30 can be identified by using this data, andtherefore an increase in cost associated with improvement in the controlunit 20 is not caused.

Alternatively, data stored in the data storage unit is data in the formof functions expressing the ON times and OFF times of the multipleswitching pulses on the basis of the numbers of the multiple switchingpulses. Even if the number of switching times increases, the ON and OFFtimings of the short-circuit unit 30 can be identified by using thisdata; and because the number of control parameters to be stored in thedata storage unit 23 c is small, an expensive memory need not be used.The time and load required for reliability verification or evaluation ofthe data can be reduced so that an increase in device cost is notcaused.

Alternatively, data stored in the data storage unit is data in the formof quadratic or higher-degree approximate expressions expressing the ONtimes and OFF times of the multiple switching pulses. Even if the numberof switching times increases, the ON and OFF timings of theshort-circuit unit 30 can be identified by using this data; and inaddition because control parameters to be stored in the data storageunit 23 c can be further reduced in number, the time and load requiredfor reliability verification or evaluation of the data can be much morereduced.

Alternatively, in data stored in the data storage unit, the change rateof the OFF times of the multiple switching pulses is greater than thatof the ON times of the multiple switching pulses. Also in the case ofusing data having the tendency of changes over time as above, the sameeffect can be produced as in the case of using data in the form ofquadratic or higher-degree approximate expressions.

Alternatively, data stored in the data storage unit is data in the formof functions expressing ON duties of the ON times of the multipleswitching pulses for the ON time of the driving signal and OFF duties ofthe OFF times of the multiple switching pulses for the ON time of thedriving signal associated with the numbers of the multiple switchingpulses. By using such data, even if the number of switching timesincreases, the ON and OFF timings of the short-circuit unit 30 can beidentified by using this data, and further because the number of controlparameters to be stored in the data storage unit 23 c is small, anexpensive memory need not be used. Thus, the time and load required forreliability verification or evaluation of the data can be reduced, andtherefore the cost does not increase.

Alternatively, data stored in the data storage unit is data in the formof quadratic or higher-degree approximate expressions expressing the ONduties and OFF duties of the multiple switching pulses. By using suchdata, even if the number of switching times increases, the ON and OFFtimings of the short-circuit unit 30 can be identified, and becausecontrol parameters to be stored in the data storage unit 23 c can befurther reduced in number, and therefore the time and load required forreliability verification or evaluation of the data can be greatlyreduced.

Alternatively, in data stored in the data storage unit, the change rateof the OFF duties of the multiple switching pulses is greater than thatof the ON duties of the multiple switching pulses. Also in the case ofusing data having the tendency of changes over time as above, the sameeffect can be produced as in the case of using data in the form ofquadratic or higher-degree approximate expressions.

Alternatively, in data stored in the data storage unit, the ON time ofthe first switching pulse in a pulse train of the multiple switchingpulses is longer than the ON times of the second and subsequentswitching pulses. The number of switching times of driving signals Sa1is reduced by using this data as compared with the case where the ONtime of the first switching pulse is set to be of the same value as theON times of the second and subsequent switching pulses, and thereforethe suppression of increase in temperature and reduction in noise arepossible because element loss is suppressed.

Alternatively, as to data stored in the data storage unit, ON duties ofthe ON times of the multiple switching pulses for the ON time of thedriving signal and OFF duties of the OFF times of the multiple switchingpulses for the ON time of the driving signal, or the ON times and OFFtimes of the multiple switching pulses are set, such that the powersupply current is within the range from an upper-limit threshold to alower-limit threshold lower than the upper-limit threshold during aperiod shorter than the half cycle of the AC power supply. With thisconfiguration, the DC output voltage Vdc can be boosted while the peaksof the power supply current Is is suppressed. Further, since the peaksof the power supply current Is can be suppressed, the distortion of thepower supply current Is when the short-circuit unit 30 is on can besuppressed, and thus harmonic components can be suppressed. Further,since the peaks of the power supply current Is can be suppressed, theflow-through period of the power supply current Is can be extended, andtherefore the power factor can be improved. Further, since the peaks ofthe power supply current Is can be suppressed, increase in the capacityof a filter circuit and the other components forming the AC power supply1 can be suppressed, and therefore increase in cost can be suppressed.

Further, the power converting device comprises the current detectingmeans that detects the power supply current; and the pulse dividing unitcorrects ON duties of the ON times of the multiple switching pulses forthe ON time of the driving signal and OFF duties of the OFF times of themultiple switching pulses for the ON time of the driving signal, or theON times and OFF times of the multiple switching pulses on the basis ofthe power supply current detected by the current detecting means individing the driving signal into multiple switching pulses by theprocessing using software. With this configuration, accuracy of the ONand OFF times of the driving signals Sa1 can be raised.

The configuration described in the above embodiment describes an exampleof the content of the present invention and can be combined with otherpublicly known techniques, and parts of the configuration can be omittedor changed without departing from the spirit of the invention.

REFERENCE SIGNS LIST

-   -   1 AC power supply    -   2 Reactor    -   3 Rectifying circuit    -   4 Smoothing capacitor    -   5 DC voltage detector    -   6 Power supply voltage detector    -   7 Current detector    -   8 Current detecting element    -   9 Current detecting means    -   10 Load    -   20 Control unit    -   21 Driving-signal generating unit    -   22 Pulse transmission unit    -   23 Pulse dividing unit    -   23 a First pulse dividing unit    -   23 b Second pulse dividing unit    -   23 c Data storage unit    -   23 d Selector    -   30 Short-circuit unit    -   31 Diode bridge    -   32 Short-circuit element    -   100 Power converting device.

The invention claimed is:
 1. A power converting device comprising: arectifier circuit that converts alternating-current power from analternating-current power supply into direct-current power; ashort-circuit unit that short-circuits the alternating-current powersupply via a reactor connected between the alternating-current powersupply and the rectifier circuit; and a control unit that controls anON/OFF operation of the short-circuit unit during a half cycle of thealternating-current power supply, wherein the control unit includes: adriving-signal generating unit that generates a driving signal that is aswitching pulse for controlling the ON/OFF operation of theshort-circuit unit; and a pulse dividing unit that divides the drivingsignal into a plurality of switching pulses so that peak values of powersupply current of the alternating-current power supply are within therange from an upper-limit threshold to a lower-limit threshold lowerthan the upper-limit threshold.
 2. The power converting device accordingto claim 1, wherein the pulse dividing unit includes: a data storageunit that stores data used during dividing the driving signal into aplurality of switching pulses; and a first pulse dividing unit thatdivides the driving signal into a plurality of switching pulses on thebasis of the data stored in the data storage unit.
 3. The powerconverting device according to claim 1, wherein the pulse dividing unitincludes: a second pulse dividing unit that divides the driving signalinto a plurality of switching pulses; so that peak values of the powersupply current are within the range from an upper-limit threshold to alower-limit threshold lower than the upper-limit threshold.
 4. The powerconverting device according to claim 1, wherein the pulse dividing unitcomprises: a data storage unit that stores data used during dividing thedriving signal into a plurality of switching pulses; a first pulsedividing unit; a second pulse dividing unit that divides the drivingsignal into a plurality of switching pulses so that peak values of thepower supply current of the alternating-current power supply are withinthe range from an upper-limit threshold to a lower-limit threshold lowerthan the upper-limit threshold; and a selector that selects theswitching pulses from the first pulse dividing unit or the switchingpulses from the second pulse dividing unit so as to output.
 5. The powerconverting device according to claim 2, wherein the data stored in thedata storage unit includes the number of divisions of the drivingsignal, ON times of the plurality of switching pulses, and OFF times ofthe plurality of switching pulses.
 6. The power converting deviceaccording to claim 2, wherein the data stored in the data storage unitincludes the number of divisions for the driving signal, ON duties of ONtimes of the plurality of switching pulses for an ON time of the drivingsignal, and OFF duties of OFF times of the plurality of switching pulsesfor an ON time of the driving signal.
 7. The power converting deviceaccording to claim 2, wherein the data stored in the data storage unitis data in the form of functions expressing ON times and OFF times ofthe plurality of switching pulses on the basis of identifying numbers ofswitching pulses in the plurality of switching pulses.
 8. The powerconverting device according to claim 7, wherein the data stored in thedata storage unit is data in the form of quadratic or higher-degreeapproximate expressions expressing the ON times and OFF times of theplurality of switching pulses.
 9. The power converting device accordingto claim 8, wherein the data stored in the data storage unit is data inwhich a change rate of the OFF times of the plurality of switchingpulses is greater than a change rate of the ON times of the plurality ofswitching pulses.
 10. The power converting device according to claim 2,wherein the data stored in the data storage unit is data in the form offunctions expressing ON duties of ON times of the plurality of switchingpulses for an ON time of the driving signal and OFF duties of OFF timesof the plurality of switching pulses for the ON time of the drivingsignal associated with identifying numbers of switching pulses in theplurality of switching pulses.
 11. The power converting device accordingto claim 10, wherein the data stored in the data storage unit is data inthe form of quadratic or higher-degree approximate expressionsexpressing the ON duties and OFF duties of the plurality of switchingpulses.
 12. The power converting device according to claim 11, whereinthe data stored in the data storage unit is data in which a change rateof the OFF duties of the plurality of switching pulses is greater thanthat of the ON duties of the plurality of switching pulses.
 13. Thepower converting device according to claim 2, wherein the data stored inthe data storage unit is data in which an ON time of a first switchingpulse in a pulse train of a plurality of switching pulses is longer thanthe ON times of the second and subsequent switching pulses.
 14. Thepower converting device according to claim 2, wherein the data stored inthe data storage unit is data in which ON duties of ON times of theplurality of switching pulses for the ON time of the driving signal andin which OFF duties of OFF times of the plurality of switching pulsesfor the ON time of the driving signal are set or the ON times and OFFtimes of the plurality of switching pulses are set such that powersupply current of the alternating-current power supply is within therange from an upper-limit threshold to a lower-limit threshold that islower than the upper-limit threshold during a period shorter than a halfcycle of the alternating-current power supply.
 15. The power convertingdevice according to claim 2, comprising: a current detecting means thatdetects power supply current of the alternating-current power supply,wherein the first pulse dividing unit, during dividing of the drivingsignal into a plurality of switching pulses, corrects ON duties of ONtimes of the plurality of switching pulses for the ON time of thedriving signal and OFF duties of OFF times of the plurality of switchingpulses for the ON time of the driving signal or corrects the ON timesand OFF times of the plurality of switching pulses on a basis of thepower supply current detected by the current detecting means.
 16. Thepower converting device according to claim 1, wherein the control unitis constituted by a microcomputer.
 17. The power converting deviceaccording to claim 4, wherein the data stored in the data storage unitincludes the number of divisions of the driving signal, ON times of theplurality of switching pulses, and OFF times of the plurality ofswitching pulses.
 18. The power converting device according to claim 4,wherein the data stored in the data storage unit includes the number ofdivisions for the driving signal, ON duties of ON times of the pluralityof switching pulses for an ON time of the driving signal, and OFF dutiesof OFF times of the plurality of switching pulses for an ON time of thedriving signal.
 19. The power converting device according to claim 4,wherein the data stored in the data storage unit is data in the form offunctions expressing ON times and OFF times of the plurality ofswitching pulses on the basis of identifying numbers of switching pulsesin the plurality of switching pulses.
 20. The power converting deviceaccording to claim 19, wherein the data stored in the data storage unitis data in the form of quadratic or higher-degree approximateexpressions expressing the ON times and OFF times of the plurality ofswitching pulses.
 21. The power converting device according to claim 20,wherein the data stored in the data storage unit is data in which achange rate of the OFF times of the plurality of switching pulses isgreater than a change rate of the ON times of the plurality of switchingpulses.
 22. The power converting device according to claim 4, whereinthe data stored in the data storage unit is data in the form offunctions expressing ON duties of ON times of the plurality of switchingpulses for an ON time of the driving signal and OFF duties of OFF timesof the plurality of switching pulses for the ON time of the drivingsignal associated with identifying numbers of switching pulses in theplurality of switching pulses.
 23. The power converting device accordingto claim 22, wherein the data stored in the data storage unit is data inthe form of quadratic or higher-degree approximate expressionsexpressing the ON duties and OFF duties of the plurality of switchingpulses.
 24. The power converting device according to claim 23, whereinthe data stored in the data storage unit is data in which a change rateof the OFF duties of the plurality of switching pulses is greater thanthat of the ON duties of the plurality of switching pulses.
 25. Thepower converting device according to claim 4, wherein the data stored inthe data storage unit is data in which an ON time of a first switchingpulse in a pulse train of a plurality of switching pulses is longer thanthe ON times of the second and subsequent switching pulses.
 26. Thepower converting device according to claim 4, wherein the data stored inthe data storage unit is data in which ON duties of ON times of theplurality of switching pulses for the ON time of the driving signal andin which OFF duties of OFF times of the plurality of switching pulsesfor the ON time of the driving signal are set or the ON times and OFFtimes of the plurality of switching pulses are set such that powersupply current of the alternating-current power supply is within therange from an upper-limit threshold to a lower-limit threshold that islower than the upper-limit threshold during a period shorter than a halfcycle of the alternating-current power supply.
 27. The power convertingdevice according to claim 4, comprising: a current detecting means thatdetects power supply current of the alternating-current power supply,wherein the first pulse dividing unit, during dividing of the drivingsignal into a plurality of switching pulses, corrects ON duties of ONtimes of the plurality of switching pulses for the ON time of thedriving signal and OFF duties of OFF times of the plurality of switchingpulses for the ON time of the driving signal or corrects the ON timesand OFF times of the plurality of switching pulses on a basis of thepower supply current detected by the current detecting means.